1. Field of the Invention
This invention relates to a device for isolating stacked flat workpieces, preferably stacked tubular pieces, including a driven, web-like supporting framework that rotates on a frame. Rotating rolls are supported at equal intervals on a circle concentric with the turning axis of the rolls. Each roll is provided with a row of suction boxes. The driving gears of the rolls are rotated, in a direction opposite to the rotation direction of the supporting framework, by a spider gear fixed to the frame. Intermediate gears, through which the driving gears are rotated, are supported in the supporting framework. A stacking cartridge is placed at an external cylinder defined by the row of suction boxes in such a way that each row of suction boxes of each roll withdraws an exposed workpiece from the cartridge. A transport device placed at the external cylinder removes an isolated workpiece and further transports the same.
2. Description of Related Art
A so-called rotary feeder of this type is known from DE-PS 1,277,655. In the known feeder, a stacking cartridge for accepting a stack of workpieces is located above the external cylinder described by the suction rolls. The stack, which is to be separated into single workpieces, is supported against the suction rolls and against additional back-up rolls arranged between the suction rolls forming the same external cylinder as the suction rolls. This type of support is necessary for the known rotary feeder so that a lower exposed workpiece can be withdrawn from the stack by each suction roll.
However, since suction rolls and back-up rolls supporting a stack impact upon the stack as they pass by, the rolls unavoidably stimulate vibration in the stack. In stack production, rotary feeders are positioned in front of bottom-laying machines. Modern bottom-laying machines have a high capacity so that a rotary feeder must also operate at high speed in order to supply a bottom-laying machine with isolated tubular pieces at a correspondingly increased cadence. However, at higher speeds, a stack supported on the suction and back-up rolls of a rotary feeder tends to start vibrating so forcefully that it is no longer guaranteed that the row of suction boxes of each suction roll will securely pick up the bottom tubular piece in the front edge region of the latter. As a result, either no isolation takes place or a tubular piece to be isolated is only incompletely withdrawn, possibly in an oblique position.